Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would
be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate
that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views.
It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if
you would like to post something on RF Cafe's
page, please do.
Below are all of the forum threads, including all
the responses to the original posts.
Post subject: Phase shifting of a Signal Posted: Tue Nov 01, 2005 3:31 am
How do you shift the Phase of an analog signal.
With digital its so easy, you just put a delay of couple of usecs and you get a phase shifted signal.
How do you do it in analog?
Post subject: Analog phase shiftPosted: Tue Nov 01, 2005 2:22 pm
There are several ways of shifting the phase of an analog signal:
1. Use the appropriate length of cable: 90 degrees is one-quarter wavelength (don't forget to include the velocity factor of the cable!)
2. Artificial delay lines are also a possibility at frequencies low enough that a piece of cable would be unreasonably long. These simulate a piece of cable by series / parallel C circuits, cascaded. Other kinds of LC networks are also possible if you don't want constant time delay.
3. RC Networks: the phase shift is 45 degrees at f = 1/(2 pi RC) for a simple two-component high-pass or low-pass. More complicated networks can be used to shape phase as a function of frequency.
Obviously, some techniques (RC) are lossy, some (transmission lines) have very little loss.
Post subject: Posted: Wed Nov 02, 2005 1:37 pm
Are you aware of any manufactureres that make Delay lines for analog signals. It should be variable delay, not one of those fixed -10%, 20% delays.
Post subject: Phase ShiftPosted: Thu Nov 03, 2005 1:30 am
I haven't checked their recent catalogs, but Data Delay Devices Inc. used to make such things.
Post subject: Posted: Thu Nov 10, 2005 2:12 pm
i found a new way - using an all pass filter to delay the phase. I can change the phase by varying the resistace. Only problem is the output amplitude is not constant at my frequency - 6Mhz.
It works fine in the Khz range.